Gyratory compactor



Aug. 19, 1969 w, DUNLAP ET AL 3,461,717

GYRATORY COMPACTOR Filed March 29, 1968' 4 Sheets-Sheet 1 Tommy L J/ww INVEN'IORJ 0514M Hume! will 6 MMlLewA ATTORNEYS Aug. 19, 1969 w. A. DUNLAP ET AL 3,461,717

GYRATORY GOMPAGTOR Filed March 29, 1968 4 SheetsSheet 3 A? Wayne A. flun/a o Z/0/7e/ J M/fieryer Tom/77y L. J/mw 1 N VENTORS 46 :1 in/J & Mmhws flTTORNE YS United States Patent 3,461,717 r GYRATORY COMPACTOR Wayne A. Dunlap and Lionel J. Milberger, both Texas A. & M. University, Department of Civil Engineering, College Station, Tex. 77843; and Tommy L. Snow, Houston, Tex.; said Snow assignor to said Dunlap and said Milberger Filed Mar. 29, 1968, Ser. No. 717,139 Int. Cl. G01n 3/00 US. Cl. 73-84 12 Claims ABSTRACT OF THE DISCLOSURE A gyratory compactor for molding compactible material comprising a mold adapted to be gyrated about a fixed point near one end of the mold so that the longitudinal axis. of the mold circumscribes a cone whose vertex coincides with the fixed point with mean operably connected to the other end of the mold for tilting the mold to a desired gyratory angle while the mold is being gyrated and means for applying a desired amount of pressure longitudinally of the mold during gyration thereof.

BACKGROUND OF THE INVENTION Continuing increases in traflic volumes and in weights and tire pressures of commercial vehicles have placed increasing demands on the load carrying capacities of modern highways. Traffic compaction of the roadbed, and particularly of the granular base coarse materials which underlie the near surface of the flexible pavement, has been found to be a major cause of shear failure and road settlement. The factors influencing the performance of granular base coarse material are usually surmised from observation of field test sections of model pavements. Laboratory investigations where control of the variable factors involved could be more closely controlled than in the field have been severely restricted due to the difliculty in fabricating representative specimens of the granular materials in the laboratory.

It is therefore an object of the present invention to provide a new and improved apparatus for compacting compactible material for use in laboratory studies of the compaction characteristics of such material or com pacting material for whatever purpose desired.

It is also an object of the present invention to provide a new and improved gyratory compactor apparatus for fabricating triaxial specimens of compactible material.

It is also an object of the present invention to provide a new and improved gyratory compactor in which the angle of gyration may be varied infinitely within a given range during gyration and in which a variable compressive force may be applied to the specimen during gyration. Also, with the apparatus of the present invention, the rate of gyration may be varied during gyration and also the number of gyrations in a given sequence or cycle may be predetermined. Furthermore, the apparatus includes means for determining the work required to gyrate the specimen under a particular compressive load and through a chosen angle of gyration. Further, the apparatus of this invention includes means to determine the instantaneous height of a specimen during gyration.

It is also an object of the present invention to provide a new and improved mold for compacting material in a gyratory compactor.

elevation showing details of construction of the gyratory portion of the apparatus of this invention;

FIG. 2 is a schematic isometric 'view showing the conical path of gyration of the apparatus of this invention;

FIG. 3 is a front elevation showing the gyratory compactor of the present invention;

FIG. 4 is a side view partially in elevation and partially in section of the gyratory compactor of the present invention;

FIG. 5 is a view partially in elevation and partially in section showing the mold as well as the mold chuck apparatus of the present invention; and

FIG. 6 is a partial sectional view along line 6-6 of FIG. 5 showing details of construction of the split mold of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Briefly, as shown in FIGS. 1 and 2 of the drawings, the gyratory compactor apparatus of the present invention comprises a gyratory arm A which is provided for gyrating a mold M connected to the lower portion of such arm A about a mold base B. The upper end of the arm A is adapted to be rotated by a rotating head assembly designated generally R and which includes means for tilting or inclining the gyratory arm A and the mold M mounted thereon relative to the base B to the desired angle for gyration 0 as will be described in detail hereinafter. A hydraulic piston P or other suitable means is provided for applying a desired compressive force longitudinally of the mold M during the gyration thereof.

Considering the apparatus of the present invention in more detail as shown in FIGS. 3 and 4 of the drawings, there is a housing or support frame H which includes a table top 12 mounted on legs 13 and having a pair of laterally spaced vertical members 15 and 16 extending upwardly from the table top 12 with upper, lower, and intermediate cross members 17, 18, and 19, respectively, extending therebetween. As shown, such cross members may be secured to the vertical members 15 and 16 by means of bolts 20 or welds or other suitable connecting means, as desired. An electric motor or suitable power source 24 is mounted on a suitable base support 25 carried on the legs 13 beneath the table top 12. The motor 24 is operably connected to a speed reducer or transmission 27 having a suitable control thereon for varying the speed of gyration of the gyratory arm A as will be described. The output of the transmission 27 drives the power transmission shaft 28 which extends upwardly through an opening in the table top 12 to the upper portion of the frame or housing H.

As shown in FIG. 3, the shaft 28 is journaled in a suitable supporting member 29 mounted on the vertical member 15. A drive sprocket 31 is provided near the upper end of the power transmission shaft 28 for receiving a chain 32 which drives a second sprocket 34 mounted on the rotating head assembly H when the power transmission shaft 28 i rotated.

A gauge 40 may be provided on the power transmission shaft 28 for indicating the amount of work required for rotating or gyrating the mold M. Also, a revolution counter 42 is provided for recording or counting the number of revolutions or gyrations of the mold M. The revolution counter 42 may be operably connected to a drive pulley 44 on the power transmission shaft 28 by means of a counter drive belt 45 or by other suitable connecting means, as desired. Also, the revolution counter may be connected to a suitable switching apparatus 46 which includes a manual off-on switch 47 as well as an apparatus operably connected to the counter 42 to automatically shut 01f power to the motor 24 and stop the gyration of the arm A upon the completion of a predetermined number of revolutions.

The rotating head assembly R as best seen in FIGS. 1 and 4 of the drawings preferably comprises a drive shaft 50 which is journaled in the upper cross member 17. Such shaft 50 has a drive sprocket 34 mounted thereon for receiving the drive chain 32 for rotating the shaft 50. The lower end of the drive shaft 50 is secured to a rotating plate 60 which carries the gyratory angle adjusting mechanism for tilting or righting the longitudinal axis of the mold M either during, before, or after gyration. Normally, the angle adjusting mechanism comprises a double acting hydraulic ram 62 which is operably connected to a sperical bearing 63 mounted on a bearing rod 64. As shown, such bearing rod 64 is received in a suitable bushing 66 in the upper end of the gyrating arm A. The hydraulic ram 62 is connected to a hydraulic power unit 70 by means of suitable conduits 71 and 72. A four-way control valve 75 is provided with such conduits 71 and 72 for directing fluid pressure to either end of the ram 62 to move the spherical bearing 63 laterally in either direction to control lateral movement of the gyrating arm A during gyration. The four-way valve allows fluid to return through one of the conduits 71 and 72 when fluid under pressure is directed to the other. Also, the hydraulic systern includes suitable return line 76 for circulating hydraulic fluid from the valve 75 to the power unit 70. A pressure regulator or valve 78 is provided for adjusting the amount of pressure in the lines 71 and 72 and a pressure gauge 77 or other suitable means may be provided for indicating the pressure of the fluid in the hydraulic system. An angle adjusting screw 68 having a bumper stop 69 thereon is also provided on the rotating plate R. Such adjusting screw 68 is used to position the bumper stop 69 so as to engage the spherical bearing 63 to limit lateral movement thereof to the desired maximum deflection or angle of gyration.

Gyration arm A, as shown in FIGS. 1 and 4, preferably comprises a longitudinally extending shank or shaft 80 having a laterally extending portion 81 secured to the upper end thereof by welding or other suitable means. The bushing support 66a is carried in a suitable housing provided at the upper end of the laterally extending portion 81 for supporting the bushing 66 which receives the spherical bearing rod 64 that connects the gyratory arm C to the rotating head assembly R. As shown, the bushing 66 is positioned by the laterally extending member 81 so as to be aligned axially of the mold M whether or not it is tilted or at a right angle to the base plate B.

A mold chuck assembly designated generally as 90 is provided at the lower end of the gyrating arm A for holding the mold M which contains the material S to be compacted. As best seen in FIG. of the drawings, the mold chuck assembly 90 preferably comprises a cylindrical member formed of a cylinder split longitudinally into a pair of half sections 91 and 92 which are removably secured together by means of bolts 93 or other suitable connecting means which can be quickly and easily removed to facilitate opening of the chuck assembly 90 for insertion or removal of the mold M. As shown, the mold chuck halves 91 and '92 each have longitudinally extending ridges or flanges 94 and 95 along the straight edges thereof; such flanges having openings 94a and 95a therein for receiving the bolts or securing means 93. Also, such mold chuck is preferably provided with longitudinally spaced, circumferentially extending ribs or bands for adding strength and rigidity to the mold chuck 90. Similarly, a plurality of longitudinally spaced plates or brackets 97 is provided for mounting the mold chuck assembly 9t) on the lower end of the arm 80-.

A bracket 98 is secured to the cross member 19 for receiving one or more springs 99 which are also secured to the uppermost bracket 97 for supporting the arm A so it will be free to move laterally and longitudinally during gyration. Also, an adjustable lateral support comprising a bracket 99a welded or otherwise mounted on the leg 13 is provided for carrying a bolt 99b which has one end secured to the arm 1 and which extends through an opening in the bracket 99a. A pair of springs 99c and 99d is preferably provided around the bolt 99]) on opposite sides of the bracket 99a with a nut 99e on the bolt for adjusting the compression on the springs 99c and 99d. Thus, the gyratory arm A which carries the mold M is free to move laterally as well as longitudinally Within certain limits and with relatively smallrestraint so that the force of gyration is applied to the material and the compression from the piston P is applied to the material in the mold M.

The mold M, which is also shown in FIGS. 1 and S of the drawings, is adapted to be carried in the mold chuck assembly 90. Such mold preferably comprises a cylindrical container which is split longitudinally into a pair of half-cylindrical pieces 100 and 101 to facilitate removal of the compacted material from the mold after the compaction has been completed so as not to disturb the compacted material. A plurality of pins 103 is provided in the straight edge of one of the half cylinder pieces 101 and a plurality of corresponding holes 104 is provided in the facing edge of the other half cylinder 100 to maintain proper alignment of such half cylinder pieces with each other. Also, in the preferred embodiment of this invention, the interior wall or surface 110 of the mold is hardened to a degree of hardness which is preferably harder than the material being compacted in the mold. The inner surface 110 is also polished so as to present a low friction wall for contact by the material to be compacted to facilitate compaction of substantially the entire mass of material simultaneously and to thereby eliminate the necessity of compacting the material in layers. The interior surface 110 may be coated with a Teflon impregnated ceramic lining to provide the hard surface low friction characteristics desired. Also, in the preferred embodiment, the inner surface of the mold chuck halves 91 and 92 is precisely machined to provide a snug fit between the mold M and mold chuck 90 to thus eliminate the need for any additional external connection between the chuck and the mold.

The mold base B preferably comprises a plate 111 having a top 112 and a bottom 113 which is normally positioned on a table top -12 directly beneath the piston P and is secured in position thereon by bolts 114 or other suitable securing means, as desired. Such base plate B includes a centrally disposed conical portion 115 projecting above the top 112 which extends upwardly into the lower end of the mold M so that the upper surface 116 of the projection 115 forms a bottom for engaging the material in the cylindrical mold M. A circumferentially extending groove 117 normally extends around the projection 115 for catching any material extruded from the mold during the process of compaction, or the groove may be omitted, if desired. The outer edge 118 of the projection 115 is tapered or inclined downwardly and inwardly from the upper surface 116 to accommodate tilting of the longitudinal axis of the mold M during operation. As shown in FIG. 1, the mold M is inclined or tilted with respect to the base plate B whereas in FIG. 5 of the drawings the mold M is positioned in a vertical position at a right angle with respect to the base plate B. In either position, it is important that the lower edge of the mold halves 91 and 92 be positioned so as not to engage the botttom of the groove or depression 117. With the mold thus positioned so that the lower edges do not engage the surface 117a,

the mold will be free to gyrate about the upstanding projection and to allow the mold M to move downwardly as well as upwardly during compaction of the material therein.

An upper bearing plate 120 is shown on top of the material S and is provided with a surface 120a which may also be hardened for engaging the upper end of the material mass contained in the cylindrical mold M and for transmitting a downward thrust from the piston P to such material.

The outer edge 121 of the bearing plate 120 is tapered or inclined inwardly and upwardly at an angle of substantially the same magnitude as the angle of inclination of the outer surface 118 of the projection 115 to also accommodate lateral tilting of the mold M with respect to the piston P. The piston P which is mounted on the lower and intermediate cross members 18 and 19, respectively, is provided for imposing a compression thrust on the ma: terial S in the cylindrical mold M. In the preferred embodiment, the thrust of the piston P is at a right angle to the base plate B regardless of whether or not the mold M containing the material S is in a vertical position as shown in FIG. 5 or in an inclined or tilted position as shown in FIG. 1. Throughout the gyration of the material, the loading on the material is at a right angle with respect to the upper surface 116 and the lower surface 120a of the bearing plate 120, which surfaces are substantially parallel to each other.

The piston P is preferably actuated by hydraulic pressure supplied to the piston cylinder 122 by means of a suitable conduit 123 connected to the hydraulic power unit 70. A four-way control valve 124 is provided in the conduit 123 for directing the flow of hydraulic fluid to each end of the piston cylinder 122 for moving the piston in either direction, as desired. A pressure regulator 124a is provided in the conduit 123 for controlling the pressure of the fluid actuating the piston P and pressure gauge or indicator 128' is also preferably provided with the regulator valve 124a. Also, such hydraulic system includes suitable return lines or drain 129 to return hydraulic fluid from the valve 124 to the unit 70.

A low friction thrust head assembly 130 is provided for imparting the compressive thrust or load provided by the piston P to the upper bearing plate 120 while the mold M is being gyrated. The thrust assembly includes a head piece 131 which is secured to the piston shaft or rod 132 by set screws 133 or other suitable means. Such head 131 includes a circumferentially extending bearing groove 134 formed in its lower face 135 for receiving bearings such as needle thrust bearings 136 which engage the upper surface of the lower bearing plate 140 as will be described hereinafter. The head 131 also includes a downwardly projecting centering spline or shaft 137 which is positioned centrally of the circumferentially extending bearing groove 134. Such shaft 137 is preferably provided with needle roller bearings 138 extending circumferentially thereof and which are secured thereon by means of a snap ring 139 or other suitable securing means, as desired.

The lower bearing plate 140 is provided on the lower side of the head 131 for engaging such head 131 and also the upper bearing plate 120 provided on top of the material S in the mold M therebelow. Such lower bearing plate 140 has a central opening 141 therein for receiving the centering shaft 137 and the bearings 138 positioned thereon. The lower surface 143 of the lower bearing plate 140 is preferably provided with a pair of radially spaced O-ring grooves 144 for receiving O-rings or other suitable seals 145 which are provided for retaining grease or other lubricant in the annular space therebetween to provide a grease or lubrication cushion between the lower bearing plate 140 and the upper surface of the upper bearing plate 120 to facilitate lateral as well as rotational movement therebetween during gyration of the mold M.

In the operation of the apparatus of the present invention, the material S is placed in the mold M that is positioned in an upright position above the base plate B with the lower edge of such mold in the annular groove 117, but spaced above the surface 117a. The mold 90 is then positioned in the mold chuck, and the chuck halves 91 and 92 are firmly secured together by means of the securing bolts 93. The revolution counter 42 may be preset to shut off the power supply to the motor 24 after a desired number of revolutions of the gyratory compactor and the manual switch 47 moved to the on position to begin the gyrating of the material in the mold M. Hydraulic control valve 75 may be actuated to tilt or incline the gyrating arm A to the desired angle of inclination for gyration of the material in the mold and such angle of gyration may either remain constant throughout substantially the full cycle of gyarations, or the angle may be either increased or decreased, as desired, to any desired degree within the full operating range of the apparatus during the course of gyration of the specimen. It will also be appreciated that in order to provide a right circular cylinder of the material being compacted that during the terminal revolutions or gyrations of the material it will be necessary to right the gyrating arm A so that the longitudinal axis of the mold M is in a vertical position with respect to the base plate B. Thus, when the gyrations are completed, the upper and lower surfaces of the compacted material are substantially parallel and at a right angle to the longitudinal axis of the material mass. The number of gyrations during which the mold M is righted or moved to a vertical position may be controlled by actuating the hydraulic ram 62 during the terminal gyrations. This may be done by actuating the valve or a fluid control valve 75a in the hydraulic line 72 may be used to control the rate' of movement of the hydraulic ram 62 in positioning the mold M in a vertical position.

Also, it will be appreciated that during the course of such gyration a vertically directed force may be applied to the material S by means of the piston P and that such force may be constant or may be varied, as desired. The magnitude of the force applied by the piston P to the material S will be controlled by means of the regulator 124a and hydraulic fluid line supplying such piston P with hydraulic fluid from the hydraulic power unit 70, with the gauge or indicator 128 indicating the amount of pressure being thus applied.

It will also be appreciated that with the gyratory arm A rotatably and slidably connected at its upper end on the spherical bearing rod '64 by means of the bushing 66 and also carried on the spring supports 99, with the lower portion of the mold chuck positioned about the inverted conical projection on the base B, the gyrating arm A offers little resistance to movement by the rotating head R and also offers little resistance to the compressive forces applied by the piston P. Furthermore, with the mold M positioned so that its lower edge does not engage the surface 117a throughout the gyratory cycle, the projection acts to compress the material S from the bottom when the piston applies a compressive force thereabove. With the polished hard surfaced lining in the mold M, the mold itself offers little frictional resistance to compression of material therein to thus provide substantially uniform compaction throughout the material S. Similarly. the low friction thrust head assembly which imposes the longitudinal thrust from piston P onto the material S via the upper bearing plate 120 imposes a low lateral load on the gyratory apparatus to thereby allow for a more accurate measurement of the compactive effort required to compact the material in the mold M.

For providing an instantaneous indication of the height of the material being compacted in the mold M, a linear potentiometer or other suitable measuring means is provided. Such measuring means may be mounted on the cross member 19 or some other suitable location and is operably connected to the upper bearing plate 120 or other member which moves vertically with upper bearing 120 as the material is compacted by a cable 141 or other suitable connecting device so as to give a continuous indication of the height of the material in the mold.

It will be appreciated that the configuration of the mold M may be other than cylindrical, such as ovoid, elliptical, square, triangular, or some other shape, as desired. Also, the mold M can be formed of any desired number of segmented portions.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention.

We claim:

1. A gyratory compactor comprising:

(a) a support frame;

(b) a mold for receiving compactible material;

(c) a mold base adapted to be mounted on said frame;

(d) a gyratory arm;

(e) means for supporting said arm above the base;

(f) a chuck connected to one end of said arm for positioning a mold therein above said base;

(g) rotatable support means carried on said frame for rotating the other end of said arm with respect to said base; and

(h) means for compressing the compactible material in said mold during gyration thereof.

2. The invention of claim 1 wherein said mold comprises a plurality of segmented members each means thereon for aligning each of said segmented members with the other.

3. The invention of claim 1 wherein the inner surface of said mold is hardened and polished to provide a hard low friction surface for contact by the material being compacted therein to facilitate substantially uniform compaction throughout the material.

4. The invention of claim 1 wherein said mold base comprises a base plate having an inverted conical upstanding projection thereon for extending into one end of said mold for engaging the compactible material therein.

5. The invention of claim 4 wherein said mold base includes a circumferentially extending recess extending around said projection for receiving material extruded from said mold.

6. The invention of claim 1 wherein said means for supporting the arm include spring means suspending said 8 arm from said frame so as to permit said arm to be inclined relative to said base plate and to permit longitudinal movement of said arm with respect to said base plate.

7. The invention of claim 1 wherein said rotatable support means includes means for varying the angle of gyration of said mold With respect to said base before, during, and after gyration so as to increase or decrease the gyratory angle in any desired sequence.

8. The invention of claim 1 including means for determining the amount of work required to gyrate the mold.

9. The invention of claim 1 including means for predetermining the number of gyrations of the mold.

10. The invention of claim 1 including means for varying the compressive load on the material in the mold during gyration thereof.

11. The invention of claim 1 including means for providing an instantaneous indication of the height of the material in the mold during gyration thereof.

12. The invention of claim 1 including means for varying the rate of gyration of the mold.

References Cited UNITED STATES PATENTS 2,531,388 11/1950 Black 7384 X 2,972,249 2/1961 McRae et a1. 7388 3,161,044 12/1964 Harrison et al. 10099 X RICHARD C. QUEISSER, Primary Examiner JERRY W. MYRACLE, Assistant Examiner U.S. Cl. X.R. l00-99 

